Abstract : The French EPC (Energy Performance Certificate) was implemented in 2006 to be mandatory for selling or renting a dwelling. From the beginning, the EPC's robustness was questioned. Field tests showed that, for the same building, two different energy labels could be obtained from auditors. Thus in 2012 the EPC was revised to make it more reliable by, among others , doubling the number of inputs in the calculation method. Unfortunately, recent investigations show that the problems persist whereas a law plans to make EPC enforceable against third persons in 2021. In this way, the French government has announced a new rework of the EPC for 2019. In this context we study the part in the dispersion of EPC's results due to the calculation method. In 2011 a first study consisted of an uncertainty propagation (Monte-Carlo method) and a sensitivity analysis in the initial version of the calculation method (2006 method) on the case of a single-family house. Using the same case and the same methodology (and also Sobol method), we are able to compare the differences between the initial and revised calculation methods. The revised version is not more accurate and some main sources of dispersion in the EPC's results are identified: • in all input modes, estimated energy consumption has increased while the EPC is known to overestimate actual consumption , • we observed a doubling of consumption's dispersion, • significant differences in results exist between the input modes ("precise input" vs. "default value" with threshold effects in the value tables), • a large part of discrepancy depends on the uncertainties on transmission coefficients of the thermal insulation and on the surface area. In conclusion, in association with the question of the qualification of diagnosticians, the calculation method must be deeply reworked so that the EPC becomes the main tool of the building stock refurbishment.